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Background  Born December 18, 1856 in Cheetham Hill, England.  His parents were Joseph James Thomson and Emma Swindells  He had one brother Frederick Vernon Thomson

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Education  Thomson’s early education was in small private schools.  His parents wanted him to become an apprentice engineer to Sharp-Stewart & Co. but, in 1870 at the age of 14 he was admitted to Owens College.  1876 J.J. moved to Trinity College and four years later obtained his BA in mathematics.  In 1883 he received a masters degree.

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Professor Thompson  In 1884 at age 28, Thomson became Cavendish Professor of Physics at University of Cambridge.  Cambridge is where he taught Earnest Rutherford and did all of his research on electrons.

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Discovery of the Electron  Although some scientists had said that atoms were made up of a more fundamental particle roughly the size of a hydrogen atom, in 1897 Thompson was the first to state that they were much smaller than that…about a thousand times smaller.  He biased this statement on the fact that the rays coming off of atoms, cathode rays, could travel much further than a hydrogen atom.

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Discovery of the Electron  Cathode Ray experiments.  By applying an electric field to these rays Thompson found that he could bend the rays and they bent away from the negative so, they were in fact negatively charged.  Thomson could also measure the angle they were deflected and calculate the ratio of the electrical charge to the actual mass of the particles.  He also found that the mass of these particles was constant no matter what gas they came off of.

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Discovery of the Electron  With the cathode ray experiments Thompson concluded that atoms were divisible in to a much smaller particle.  He originally called these particles corpuscles.  With this knowledge of electrons, or corpuscles as he still called them, he went on to develop a new model of the atom.

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Plum Pudding Model  In 1904 Thomson proposed that an atom is made up of electrons surrounded by a ball of positive charge. This keeps the whole atom having a neutral charge.  He named this the plum pudding model because of its similarity to the raisin electrons surrounded by the positive breading.

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Isotopes  In 1912 during Thomson's work with his assistant F.W. Aston on the composition of canal rays he channeled a stream of ionized neon through a magnetic and electric field and observed two patches of light on the photographic plate.  They concluded that since there were two different paths the atom took there must be two neon atom of differing mass present in their sample, two isotopes of neon.

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Thomson’s Other Achievements  1905 Thomson discovered the natural radioactivity of potassium.  1906 Thomson demonstrated that hydrogen only has a single electron per atom.

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Personal Life and Honors  Thomson married one of his students at Cambridge; Rose Elisabeth Paget. They had two children, a daughter, Joan Paget Thomson and a son, George Paget Thomson.  He was honored several times for his work in physics.  1906 Nobel Prize  1908 Knighted by King Edward VII  Honorary Doctorate degrees from 21 Universities including Philadelphia University.  In 1918 Thomson left research and became Master of Trinity College until shortly before his death on August 30, 1940.